Help! Can I play with forge installed with mods that are not compatible with forge.
Depends on the mod and the version of Minecraft. If by not compatible you mean doesn't use Forge, like Optifine or the shaders mod, some mods are able to be loaded by Forge even though they base edit, obviously Optifine and the shaders mod are two that can be loaded by Forge (else I wouldn't have listed them). LiteLoader mods can be installed alongside by download the Forge-compatible LiteLoader builds and installing LiteLoader like regular Forge mods. However, 1.8.1 or above, no Forge.
If it crashes, post the log here.
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Author of the Clarity, Serenity, Sapphire & Halcyon shader packs for Minecraft: Java Edition.